Healthy bones are the basic requirement for a vital and energetic life. Bones form the skeletal structure which provides mechanical support and flexibility to the body and serves as a reservoir of calcium, which the body draws upon to help maintain normal calcium levels in the blood.
Bones are dynamic living tissues that are not inert as thought to be. They are made up a crystalline mineral compound consisting of calcium and phosphorus known as hydroxyapatite embedded in a collagen protein framework that provides both strength and rigidity to the bones.
Through life, bones undergo cycles of resorption (removal of old bone cells) and formation of new bone cells which help maintain bone health. Maximum bone size and strength is known as the peak bone mass. Although genetic factors largely determine the size and density of your bones, lifestyle factors such as good nutrition, regular exercise, avoiding smoking and excess alcohol also play a key role.
Childhood and adolescence are the most critical phases of life for ensuring bone health as these are phases of rapid growth. In childhood and adolescence, good nutrition along with regular exercise helps build peak bone mass thereby reducing the risk of developing osteoporosis later in life. About 50 per cent of peak bone mass is built during adolescence and bone density slowly builds up until around 30 years of age, when peak bone mass is reached. Both men and women slowly begin to lose bone mass by the age of 40 and by eating a nutritious diet, younger and older adults can help preserve bone mass and strength and reduce the risk of having fractures.
The way we eat can make or break the health of our bones. Among the many nutrients obtained from food, calcium and vitamin D are critical for maintaining bone health. Others such as phosphorus, magnesium, vitamin K, vitamin C, vitamin A, fluoride, manganese, copper, zinc and protein have also been found to contribute to bone health and growth.
Calcium is the most abundant mineral element in the human body accounting for about 2 per cent of an adult’s body weight. About 99 per cent of the body’s calcium is present in the bones and teeth, the remaining 1 per cent is present in blood and is used for the muscle contraction, transmission of nerve impulses, for the blood clotting process and activation of certain enzymes.
Since the body cannot manufacture its own calcium, it has to be obtained from the diet. Calcium is absorbed in the small intestine mainly in the duodenum, in the presence of vitamin D. The absorption of calcium decreases as the level of vitamin D decreases. Similarly lactose, vitamin C and certain amino acids favour calcium absorption. Excessive amounts of phosphorus, dietary fibre, salt, phytates and oxalic acid interfere with the absorption of calcium.
On an average about 30 to 40 per cent of dietary calcium is absorbed by healthy adults. Growing children, adolescents, pregnant women and lactating women absorb about 50 to 60 per cent of dietary calcium. The efficiency of calcium absorption decreases with age. In younger women, estrogen helps deposit calcium in the bones, but as estrogen levels drop with menopause, the deposition of calcium in the bone decreases and the rate of bone resorption (loss of calcium from the bones) increases hence menopausal and post menopausal women have a higher need for calcium.
Foods rich in calcium include nachni or ragi, bengal gram or chana, horse gram or kuleeth, moth bean or matki, kidney beans or rajma, soyabean, black gram or urad almonds, sesame or til seeds, niger seeds (karlya), amaranth or rajgira seeds, milk and milk products, dry prawns, small fish with the bones, mackerel, black pomfret, green leafy vegetables, coconut palm jaggery or madachem godd.
To be continued. . .
The writer is a Consultant Nutritionist with 17 years of experience, practising at Panaji and Margao)
Nutrients that keep our bones healthy: Part I